High dynamic range functions (HDR functions) combine a first image captured during a first shutter time with a second image captured during a second shutter time, which is longer than the first shutter time, to thereby generate a composite image having a higher dynamic range from a low luminance level to a high luminance level.
In-vehicle cameras incorporate therein such a HDR function, and use the HDR function to increase the accuracy of detecting objects, such as white lines on roads and/or other vehicles. An in-vehicle camera captures images while its luminous environment changes when the corresponding vehicle is travelling. This change in luminous environment around the in-vehicle camera changes the tone of an image captured by the in-vehicle camera. This tone change may reduce the accuracy of detecting objects, such as white lines.
For addressing such a problem, Japanese Patent Application Publication No. 2016-96417 discloses a camera system installed in a vehicle. The camera system obtains information about luminous environment around the vehicle; the luminous environment changes while the vehicle is travelling. For example, the luminous environment information includes information about a daytime luminous environment and information about a nighttime luminous environment.
The camera system captures a first image during a first shutter time, and captures a second image during a second shutter time, which is longer than the first shutter time. Then, the camera system selects one of an automatic white-balance correcting task and a custom white-balance correcting task in accordance with the luminous environment to apply the selected one of the automatic white-balance correcting task and custom white-balance correcting task to each of the first image and the second image. Thereafter, the camera system combines the first image with the second image, thus generating a composite image having a higher dynamic range.